1. Limited time only! Sign up for a free 30min personal tutor trial with Chegg Tutors
    Dismiss Notice
Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Homework Help: Electric Potential and Field

  1. Oct 17, 2008 #1
    1. The problem statement, all variables and given/known data

    The potential as a function of position in a region is given by V(x) = 3x - 2x^2 - x^3. (x in meters and V in volts). Find equation for electric potential field.

    2. Relevant equations

    v = integral(E * dr)

    3. The attempt at a solution

    I tried taking the derivative of v to get E but it keeps says im missing something. So first i tried, 3-4x-3x^2 but its off by a multiple and than i figured since v is the integral of E * displacement --> meaning the derivative of V is E so i got what i got before and decided to divide by X which got me 3/x - 4 - 3x which also didnt work.

    Im not sure quite what to do.
  2. jcsd
  3. Oct 17, 2008 #2
    The electric field is given by

    [tex] E = - \vec{\nabla}V [/tex]

    In this case,

    [tex] E = -\frac{dV}{dx} [/tex]

    Your forgetting the minus sign.
  4. Oct 17, 2008 #3
    ah ok ;) makes sense.

Share this great discussion with others via Reddit, Google+, Twitter, or Facebook